Crosslinkable Moulding Composition

Abstract

A crosslinkable moulding composition comprises: (1) a functionalised isocyanate product having at least six ethylenically unsaturated groups which is the reaction product of (i) an isocyanate component having an isocyanate functionality of two or more, and (ii) an ethylenically unsaturated component having at least one functional group that is reactive with an isocyanate group of the isocyanate component and at least two ethylenically unsaturated groups; and (2) a monomer component comprising a cross-linking monomer having at least two ethylenically unsaturated groups, wherein at least one of an ethylenically unsaturated component (ii) and / or a monomer component (2) are selected to have at least three ethylenically unsaturated groups. The moulding compositions are especially suitable for reinforcement and thermal curing. Example crosslinked resins derived from such moulding compositions are shown to be capable of achieving high heat deflection temperatures, often in excess of 260° C.

Description

[0001]The present invention relates generally to a thermosetting resin composition and a cured resin derived from such a composition. In particular, the present invention is concerned with a thermosetting resin composition based on a functionalised isocyanate monomer for use in moulding. The invention provides moulding compositions for reinforcement for use in making shaped articles including laminates, and methods of making such resins and articles.[0002]Thermosetting resins curable by a free radical copolymerisation process are well known. Examples of such are unsaturated polyester resins and so-called vinyl ester resins. In both cases, a polymer containing ethylenically unsaturated groups such as fumarate or methacrylate is dissolved in a copolymerisable monomer such as styrene. Such resins are liquid under normal conditions but, when treated with a source of free radicals such as an organic peroxide initiator, will rapidly crosslink to form a hard thermoset plastic mass. Such a ...

AI Technical Summary

Benefits of technology

[0005]HDT can be increased by raising the number of ethylenically unsaturated groups in either or both of the polymer and copolymerisable monomer(s) making up the resin, giving a higher crosslink density in the finished article. However, a higher crosslink density also makes the finished article more brittle, such that its mechanical performance is impaired. In particular, articles made from high crosslink density resins exhibit low strain to failure in either tension or bending and therefore are of low strength.

[0244]The present inventor has found that a post curing step can be beneficial in achieving high HDT and good tensile and flexural properties.

Problems solved by technology

However, a higher crosslink density also makes the finished article more brittle, such that its mechanical performance is impaired.

In particular, articles made from high crosslink density resins exhibit low strain to failure in either tension or bending and therefore are of low strength.

Consequently, it has proved difficult to extend the use of thermoset plastics into many applications in which the finished article will be exposed to high temperatures (e.g. in excess of 200° C.) and significant mechanical stress, because of, on the one hand, the comparatively low heat deflection temperatures offered by traditional thermosetting resins and, on the other hand, the inferior mechanical properties resulting from the use of resins designed to give a high crosslink density in order to attain a high HDT.

Furthermore, the mechanical properties of such curable resins when combined with a reinforcing component such as a fibre, are difficult to predict.

For example, a resin having a desirable HDT may, when reinforced, possess insufficient tensile and flexural strength to make it useful for forming shaped articles, particularly if those articles are to be subjected to significant loads.

However, the HDT obtainable may be limited by the postcure temperature to which it is possible to expose the shaped article.

These resins, however, require curing at temperatures in excess of 300° C. to attain their maximum heat resistances, the curing process also requiring pressures significantly above normal atmospheric pressures.

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